1. Field of the Invention
The present invention relates to the field of cryptography. More particularly, the present invention relates to a cryptographic device which translates encrypted information from one encrypted format to another without unsecured exposure of its non-encrypted format.
2. Description of Art Related to the Invention
In today's society, it is becoming more and more desirable to transmit digital information (i.e., data, control or address) from one location to another in a manner which is clear and unambiguous to a targeted recipient, but incomprehensible to any illegitimate interlopers. Accordingly, before transmission, the digital information is typically encrypted by a host processor executing an encryption algorithm stored in main memory. A communication key specific to a targeted recipient is used for such encryption. Thereafter, the targeted recipient decrypts the encrypted information for his or her own use. This conventional cryptographic transmission technique is commonly used in governmental applications as well as for commercial applications where sensitive information (e.g., confidential, proprietary, etc.) is being transmitted.
Likewise, it is further becoming desirable to store digital information in an encrypted format within main memory or a mass storage device associated with a computer. This is done to prevent an unauthorized person from downloading sensitive information in a non-encrypted format (i.e., plain text) from main memory or a mass storage device onto a floppy disk. However, neither the storage of information in an encrypted format nor the conventional cryptographic transmission technique fully protects plain text from unsecured exposure (i.e., outside the confines of the element executing the cryptographic algorithm). For example, in order to transfer an encrypted document from one computer to another, the encrypted document would be decrypted to plain text and re-encrypted with a communication key specific to the targeted recipient. Thus, the plain text will be exposed at least on the system bus and, in those cases where the document is greater in size than main memory, the plain text might be temporarily stored on the computer's mass storage device (e.g., internal hard disk). This exposure problem poses a number of disadvantages associated with security.
One clear disadvantage is that plain text may be readable by an unauthorized person in those situations where it is not immediately removed from the internal hard disk or the hard disk is accessible to other computers through a local area network. Even if the sender diligently removes the plain text from the hard disk or the document as plain text is never stored on the hard disk, there is a possibility that an interloper may gain access to the plain text by simply monitoring the system bus of the computer through software (e.g., computer-virus) or hardware means (e.g., logic analyzer).
Another disadvantage is that there is no mechanism to guarantee that only the intended recipient can read the contents of a message when the message is sent in an encrypted format to a third party (e.g., system administrator) who is responsible for re-encrypting the message with a different encrypted format.
Yet another disadvantage is that there is no mechanism to protect against unauthorized use of data provided through content distribution or by software packages (i.e., copy protection).
Hence, it would be desirable to create a cryptographic device that sufficiently mitigates access to information in a non-encrypted format (i.e., plain text) originally contained within one source in one encrypted format and needs to be transferred to another source through another or even the same encrypted format. The cryptographic device would virtually eliminate any interlopers from stealing secure information because the interloper would have to obtain that information from integrated circuits inside the chip package which is clearly more difficult than obtaining information from bus lines.